I think a lot of people just don’t want to be bothered. They look at parenthood as a big hassle without realizing the joys that come with it—that it is part of a full life. They would rather have free time, expensive cars & clothes, and exotic vacations. In short, materialism is their new G-d.
Re your post 16, you are generalizing (and all generalities are wrong—including this one). Seriously, though, I take issue with your statement that people choose to not have children because they are materialistic.
This may play a role in a few cases but I submit that that is a tiny minority viewpoint. I think that a majority of the decisions to not have children is that the would-be parents do not see their society as being worthwhile in which to bring up children. Would you want to bring a child into this world at this red-hot minute, knowing that the child would grow up in a likely socialistic society, with all the limitations on being able to prosper, the poor health care that is just over the horizon, and other problems inherent in such a society? Long sentence, I’m afraid. Sorry.
Anyway, don’t assume that because someone doesn’t want children, that they are selfish bastards. People have their reasons.
There also seems to be a very extended adolescence in most western countries including ours. Too much importance put on fun and personal freedom.